System and method of iris-pupil contrast enhancement

ABSTRACT

System and method of photoaltering a region of an eye using an enhanced contrast between the iris and the pupil of the imaged eye. The system includes a laser assembly outputting a pulsed laser beam, a user interface displaying one of a first digital image of the eye and a second digital image of the eye, and a controller coupled to the laser assembly and the user interface. The first digital image has a first contrast between the pupil and the iris, and the second digital image has a second contrast between the pupil and the iris. The controller selectively increases the first contrast between the pupil and the iris to the second contrast between the pupil and the iris and directs the pulsed laser beam to the region of the eye based on one of the first and second digital images.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of and claims priority to U.S.application Ser. No. 12/416,346, filed Apr. 1, 2009, which claims thebenefit of U.S. Provisional Application No. 61/041,547, filed Apr. 1,2008, the entire contents of which are hereby incorporated in itsentirety for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION Field of the Invention

The field of the present invention is generally related to ophthalmiclaser systems and more particularly, to apparatus, systems, and methodsof iris-pupil contrast enhancement in ophthalmic laser surgery.

Background

In current ophthalmic laser surgery procedures, a combination of opticalmicroscopes and directed light from a light source is used to view thepatient's eye. These optical microscopes typically use refractive lensesto focus light into the viewer's eye or another light detector. Morerecently, image sensors, such as photoelectric light sensor arrays usingcharge coupled devices (CCDs) (e.g., complementary metal oxidesemiconductor (CMOS) sensors), have been developed and capture digitalimages. When implemented as a digital camera, the digital camera cancapture images of the patient's eye.

Centration or alignment of the laser and laser output with the patient'seye is typically a preliminary step for most ophthalmic laser surgeryprocedures. In general, centration or alignment with the patient's eyeis accomplished using the image of the patient's eye and, to someextent, delineating the pupil from the iris. The light intensity orlight source direction (e.g., in relation to the eye) may be modified toimprove the overall brightness of the imaged eye including both thepupil and iris. Additionally, some displays have a general contrastcontrol to vary the contrast of the entire displayed image to somedegree. These techniques may be helpful to delineate the pupil from theiris for lighter eye colors (i.e., lighter iris color). When imaging theeye with a digital camera or other image sensor based device,delineating the pupil from the iris for darker-colored eyes (e.g.,brown-colored eyes appear darker than blue-colored eyes) may bedifficult and thus, interfere with centration or alignment using theresulting imaged patient's eye. For example, the difference inbrightness between a brown-colored iris and a black-colored pupil ismuch less than the difference in brightness between a blue-colored irisand a black-colored pupil. Changing the light intensity or light sourcedirection or adjusting conventional contrast controls on displays maynot sufficiently differentiate the brightness between the brown-colorediris and the black-colored pupil. Additionally, conventional digitalvideo cameras have relatively limited resolution. While images fromthese conventional digital video cameras may be magnified, the imagedetail decreased with magnification. Thus, the effective imagemagnification capabilities of conventional digital video cameras arelimited (e.g., for delineating the pupil from the iris fordarker-colored eyes).

Accordingly, it is desirable to provide an ophthalmic surgical systemand a method of ophthalmic laser surgery that improves centration oralignment with the eye. It is also desirable to provide an ophthalmicsurgical system and a method of ophthalmic laser surgery thatselectively enhances the contrast of an imaged eye. Additionally, otherdesirable features and characteristics of the present invention willbecome apparent from the subsequent detailed description and theappended claims, taken in conjunction with the accompanying drawings andthe foregoing technical field and background.

SUMMARY OF THE INVENTION

The present invention is directed towards photoaltering a region of aneye using an enhanced contrast between the iris and pupil of the imagedeye. In one embodiment, a system is provided including a laser assemblyconfigured to output a pulsed laser beam, a user interface configured todisplay one of a first digital image of the eye and a second digitalimage of the eye, and a controller coupled to the laser assembly and theuser interface. The first digital image has a first contrast between thepupil and the iris, and the second digital image has a second contrastbetween the pupil and the iris. The controller is configured toselectively increase the first contrast between the pupil and the iristo the second contrast between the pupil and the iris and direct thepulsed laser beam to the region of the eye based on one of the first andsecond digital images.

In another embodiment, a method is provided including producing a firstdigital image of the eye, selectively increasing a first contrastbetween the iris and the pupil to a second contrast between the iris andthe pupil, displaying a second digital image of the eye, centrating theeye based on the second contrast, and directing a pulsed laser beam atthe region. The first digital image has the first contrast between theiris and the pupil, and the second digital image has the secondcontrast.

In another embodiment, a computer system is provided including aprocessor, and a memory storing computer readable instructions that whenexecuted by the processor cause the computer system to perform a methodof photoaltering a region of an eye. The method includes producing afirst digital image of the eye, selectively increasing a first contrastbetween the iris and the pupil to a second contrast, displaying a seconddigital image of the eye, centrating the eye based on the secondcontrast between the iris and the pupil, and directing the pulsed laserbeam at the region. The first digital image has the first contrastbetween the iris and the pupil, and the second digital image has thesecond contrast.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like reference numerals refer to similarcomponents:

FIG. 1 is a block diagram of a system for photoaltering a region of aneye in accordance with one embodiment of the present invention;

FIG. 2 is a block diagram of an ophthalmic laser system in accordancewith one embodiment;

FIG. 3 is a block diagram of an interface system and the imaging systemshown in FIGS. 1 and 2 in accordance with one embodiment of the presentinvention;

FIG. 4 is a front view of a graphical user interface in accordance withone embodiment; and

FIG. 5 is a flow diagram of a method for photoaltering a desired regionof an eye in accordance with one embodiment.

DETAILED DESCRIPTION

The present invention generally provides systems and methods forphotoaltering (e.g., using a laser) a desired region of the eye (e.g., asub-surface region of the eye, such as within the corneal epithelium andon or within Bowman's layer, the stroma, Descemet's membrane, theendothelium, or the like) with an enhanced imaging component. Examplesof photoalteration include, but are not necessarily limited to, chemicaland physical alterations, chemical and physical breakdown,disintegration, ablation, vaporization, or the like. Using a digitalimage of the eye, an operator aligns and/or centrates the laser with thedesired region prior to directing pulsed laser beams to the desiredregion. At times, the operator may desire an enhanced image of the eyethan provided in the initial digital image. In one embodiment, thesystem increases the contrast between the iris and pupil displayed inthe digital image of the eye in response to an operator selectedfunction. For example, a dark/light eye function may be provided to theoperator on a display, as a separate component of the system, orotherwise available for selection by the operator via an input device.For darker colored eyes, the operator can select the dark/light eyefunction to increase the contrast between the iris and pupil displayedin the digital image and thereby improve the appearance of the digitalimage for alignment and/or centration (e.g., using a graphical aidoverlaying the digital image) of the eye.

Referring to the drawings, a system 10 for photoaltering a desiredregion 12 of an eye is shown in FIG. 1. The system 10 is suitable forophthalmic applications but may be used to photoalter a variety ofmaterials (e.g., organic, inorganic, or a combination thereof). In oneembodiment, the system 10 includes, but is not necessarily limited to, alaser 14 capable of generating a pulsed laser beam 18, an energy controlmodule 16 for varying the pulse energy of the pulsed laser beam 18, ascanner 20, a controller 22, a user interface 32, an imaging system 34,and focusing optics 28 for directing the pulsed laser beam 18 from thelaser 14 on the surface of or within the region 12 (e.g., sub-surface).The controller 22 communicates with the scanner 20 and/or focusingoptics 28 to direct a focal point 30 of the pulsed laser beam onto orinto the material 12. To impart at least a portion of this control,software (e.g., instrument software, and the like), firmware, or thelike, can be used to command the actions and placement of the scanner 20via a motion control system, such as a closed-loop proportional integralderivative (PID) control system. In this embodiment, the system 10further includes a beam splitter 26 and a detector 24 coupled to thecontroller 22 to provide a feedback control mechanism for the pulsedlaser beam 18. The beam splitter 26 and detector 24 may be omitted inother embodiments, for example, with different control mechanisms.

One example of photoalteration using pulsed laser beams is thephotodisruption (e.g., via laser induced optical breakdown). Localizedphotodisruptions can be placed at or below the surface of the materialto produce high-precision material processing. For example, amicro-optics scanning system may be used to scan the pulsed laser beamto produce an incision in the material, create a flap of material,create a pocket within the material, form removable structures of thematerial, and the like. The term “scan” or “scanning” refers to themovement of the focal point of the pulsed laser beam along a desiredpath or in a desired pattern.

To provide the pulsed laser beam, the laser 14 may utilize a chirpedpulse laser amplification system, such as described in U.S. Pat. No.RE37,585, for photoalteration. U.S. Pat. Publication No. 2004/0243111also describes other methods of photoalteration. Other devices orsystems may be used to generate pulsed laser beams. For example,non-ultraviolet (UV), ultrashort pulsed laser technology can producepulsed laser beams having pulse durations measured in femtoseconds. Someof the non-UV, ultrashort pulsed laser technology may be used inophthalmic applications. For example, U.S. Pat. No. 5,993,438 disclosesa device for performing ophthalmic surgical procedures to effecthigh-accuracy corrections of optical aberrations. U.S. Pat. No.5,993,438 discloses an intrastromal photodisruption technique forreshaping the cornea using a non-UV, ultrashort (e.g., femtosecond pulseduration), pulsed laser beam that propagates through corneal tissue andis focused at a point below the surface of the cornea to photodisruptstromal tissue at the focal point.

The system 10 is capable of generating the pulsed laser beam 18 withphysical characteristics similar to those of the laser beams generatedby a laser system disclosed in U.S. Pat. Nos. 4,764,930, 5,993,438, orthe like. For example, the system 10 can produce a non-UV, ultrashortpulsed laser beam for use as an incising laser beam. This pulsed laserbeam preferably has laser pulses with durations as long as a fewnanoseconds or as short as a few femtoseconds. For intrastromalphotodisruption of the tissue, the pulsed laser beam 18 has a wavelengththat permits the pulsed laser beam 18 to pass through the cornea withoutabsorption by the corneal tissue. The wavelength of the pulsed laserbeam 18 is generally in the range of about 3 μm to about 1.9 nm,preferably between about 400 nm to about 3000 nm, and the irradiance ofthe pulsed laser beam 18 for accomplishing photodisruption of stromaltissues at the focal point is greater than the threshold for opticalbreakdown of the tissue. Although a non-UV, ultrashort pulsed laser beamis described in this embodiment, the laser 14 produces a laser beam withother pulse durations and different wavelengths in other embodiments.

In this embodiment, the focusing optics 28 direct the pulsed laser beam18 toward the eye (e.g., onto the cornea) for plasma mediated (e.g.,non-UV) photoablation of superficial tissue, or into the stroma forintrastromal photodisruption of tissue. The system 10 may also includean applanation lens (not shown) to flatten the cornea prior to scanningthe pulsed laser beam 18 toward the eye. A curved, or non-planar, lensmay substitute this applanation lens to contact the cornea in otherembodiments.

The user interface 32 provides a flexible and simple environment for theoperator to interact with the system 10. In one embodiment, the userinterface 32 graphically displays (e.g., using a flat panel display orthe like) information, such as from the instrument software controllingthe operation of various components of the system 10, and provides avisual interface between the system 10 and the operator for inputtingcommands and data associated with the various components of the system.A graphical user interface (GUI) is preferably used with the userinterface 32 employing menus, buttons, and other graphicalrepresentations that display a variety of selectable functions to beperformed by the system 10 following selection. For example, theoperator may point to an object and select the object by clicking on theobject, touching a pre-designated region of a touch-screen displayingthe GUI, or the like. Additional items may be presented on the GUI foroperator selection, such as a button or menu item indicating anavailable sub-menu (e.g., a drop-down sub-menu). The user interface 32may also utilize one or more of a variety of input devices including,but not necessarily limited to, a keyboard, a trackball, a mouse, atouch-pad, a touch-sensitive screen, a joystick, a variable focal lengthswitch, a footswitch, and the like.

In addition to the user interface 32, the imaging system 34 displays amagnified real-time digital image of the patient's eye and provides aninterface for viewing the patient's eye and operator control of thecentration or alignment of the laser output with the patient's eye. Inone embodiment, an alignment or centration aid is displayed by theimaging system 34 overlaying the digital image of the patient's eye. Theaid corresponds with the position of laser output with reference to thepatient's eye. As part of the photoalteration process, the output of thelaser 14 is preferably aligned with the desired region 12 of the eye.For example, the output of the laser 14 may be substantially centeredwith reference to the pupil and iris of the patient's eye. Viewing thedigital image displayed by the imaging system 34, the operator cancenter the aid based on the pupil and the iris of the patient's eye andthereby adjust the position of the laser output. To facilitate thisalignment or centration process, the operator may desire a greatercontrast between the iris and the pupil than shown in digital image ofthe patient's eye displayed by the imaging system 34.

In one embodiment, a user selectable dark/light eye function (e.g.,represented as an icon, button, or the like) is provided (e.g., as apart of the imaging system 34, the user interface 32, or the system 10).When selected or activated (e.g., by touch), portions of the patient'seye that are normally darker in appearance in the digital image aredisplayed by the imaging system 34 with greater contrast (e.g.,sufficient contrast to delineate each of the darker portions of thepatient's eye. For example, for a brown iris and black pupil combinationof a patient eye, the brown iris and black pupil are both relativelydarker portions of the digitally imaged eye (e.g., in comparison with alighter scleral portion of the digitally imaged eye). By selecting thedark/light eye function, the imaging system 34 displays a digital imageof the patient's eye with greater contrast between the brown iris andthe black pupil in the digital image, for example.

After alignment or centration, the system 10 directs the pulsed laserbeam 18 to the desired region 12 of the eye. Movement of the focal pointof the pulsed laser beam 18 is accomplished via the scanner 20 inresponse to the controller 22. The step rate at which the focal point ismoved is referred to herein as the scan rate. For example, the scanner20 can operate at scan rates between about 10 kHz and about 400 kHz, orat any other desired scan rate. In one embodiment, the scanner 20generally moves the focal point of the pulsed laser beam 18 through thedesired scan pattern at a substantially constant scan rate whilemaintaining a substantially constant separation between adjacent focalpoints of the pulsed laser beam 18. Further details of laser scannersare known in the art, such as described, for example, in U.S. Pat. No.5,549,632, the entire disclosure of which is incorporated herein byreference.

In one embodiment, the scanner 20 utilizes a pair of scanning mirrors orother optics (not shown) to angularly deflect and scan the pulsed laserbeam 18. For example, scanning mirrors driven by galvanometers may beemployed where each of the mirrors scans the pulsed laser beam 18 alongone of two orthogonal axes. A focusing objective (not shown), whetherone lens or several lenses, images the pulsed laser beam 18 onto a focalplane of the system 10. The focal point 30 of the pulsed laser beam 18may thus be scanned in two dimensions (e.g., the x-axis and the y-axis)within the focal plane of the system 10. Scanning along the thirddimension, i.e., moving the focal plane along an optical axis (e.g., thez-axis), may be achieved by moving the focusing objective, or one ormore lenses within the focusing objective, along the optical axis.

To create a flap, the pulsed laser beam 18 is typically scanned along inthe desired region 12 using one or more patterns (e.g., a spiralpattern, a raster pattern, and the like) or combinations of patterns.When preparing a cornea for flap separation, for example, a circulararea, oval area, or other shaped area may be scanned using a scanpattern driven by the scanning mirrors. The pulsed laser beam 18photoalters the stromal tissue as the focal point 30 of the pulsed laserbeam 18 is scanned along a corneal bed. The scan rates may be selectedfrom a range between about 30 MHz and about 1 GHz with a pulse width ina range between about 300 picoseconds and about 10 femtoseconds,although other scan rates and pulse widths may be used.

The system 10 may additionally acquire detailed information aboutoptical aberrations to be corrected, at least in part, using the system10. Examples of such detailed information include, but are notnecessarily limited to, the extent of the desired correction, and thelocation in the cornea of the eye associated with the correction (e.g.,where the correction can be made most effectively). The refractive powerof the cornea may be used to indicate corrections. Wavefront analysistechniques, made possible by devices such as a Hartmann-Shack typesensor (not shown), can be used to generate maps of corneal refractivepower. Other wavefront analysis techniques and sensors may also be used.The maps of corneal refractive power, or similar refractive powerinformation provided by other means, such as corneal topographs or thelike, can then be used to identify and locate the optical aberrations ofthe cornea that require correction. The amount of photoalteration can bebased on the refractive power map.

One example of an ophthalmic scanning application is a laser assistedin-situ keratomilieusis (LASIK) type procedure where a flap is cut fromthe cornea to establish extracorporeal access to the tissue that is tobe photoaltered. The flap may be created using random scanning or one ormore scan patterns. A sidecut is created around a desired perimeter ofthe flap such that the ends of the sidecut terminate, withoutintersection, to leave an uncut segment. This uncut segment serves as ahinge for the flap. The flap is separated from the underlying stromaltissue by scanning the laser focal point across a resection bed, theperimeter of which is approximately defined by the sidecut. In oneembodiment, the perimeter of the resection bed is greater than theperimeter of the anterior surface of the flap to form a wedge-shapedflap edge. Once this access has been achieved, photoalteration iscompleted, and the residual fragments of the photoaltered tissue areremoved from the cornea. In another embodiment, intrastromal tissue maybe photoaltered by the system 10 so as to create an isolated lenticle ofintrastromal tissue. The lenticle of tissue can then be removed from thecornea.

FIG. 2 is a block diagram of an ophthalmic laser system 40 in accordancewith one embodiment of the present invention. Referring to FIGS. 1 and2, the ophthalmic laser system 40 includes, but is not necessarilylimited to, a laser source 42 providing a pulsed laser beam (e.g., thepulsed laser beam 18), a beam monitoring and processing module 44, abeam delivery module 46 coupled to the beam monitoring and processingmodule 44, the user interface 32, and the imaging system 34. The pulsedlaser beam is supplied to the beam monitoring and processing module 44where the pulse energy, the focal point separation, and optionally theminimum sub-surface depth of the pulsed laser beam are controlled. Thebeam delivery module 46 scans the pulsed laser beam along a desired scanregion. In this embodiment, the ophthalmic laser system 40 can becoupled to an eye 31 via a patient interface 33, and the patientinterface 33 may be coupled to the ophthalmic laser system 40 at amoveable loading deck 35, for example. The configuration of theophthalmic laser system 40 may vary as well as the organization of thevarious components and/or sub-components of the ophthalmic laser system40. For example, some components of the beam delivery module 46 may beincorporated with the beam monitoring and processing module 44 and viceversa.

The user interface 32 is coupled to the beam delivery module 45, and avariety of system parameters may be input or modified by the operatorvia the user interface 32 to control the beam properties and thusproduce the desired photoalteration. For example, the user interface 32may include a display presenting a graphical user interface with thevarious system parameters and an input device (not shown) for selectingor modifying one or more of these parameters. The number and type ofsystem parameters vary for each type of ophthalmic procedure (e.g., flapcreation, photorefractive keratectomy (PRK), LASIK, laser assistedsub-epithelium keratomileusis (LASEK), corneal pocket creation, cornealtransplant, corneal implant, corneal onlay, and the like).

In one embodiment, the operating pulse energy and operating focal pointseparation of the pulsed laser beam may be input or selected by theoperator via the user interface 48. For flap creation, the operator isprompted via the user interface 48 with a selection of flap patternparameters (e.g., upper flap diameter, depth of incision in cornea,hinge angle, hinge position, and the like). The parameters may bedisplayed as default values for selective modification by the operator.Additional parameters may also be displayed by the user interface 48 fordifferent procedures using the system 40. For example, a variety ofpre-programmed ring pattern parameters (e.g., inner ring diameter, outerring diameter, cornea thickness, incision axis, and the like) areprovided for corneal ring implant procedures.

In response to the system parameters selected or input via the userinterface 48, the beam monitoring and processing module 44 and/or thebeam delivery module 46 produce a pulsed laser beam with thecorresponding properties. In one embodiment, the beam monitoring andprocessing module 44 includes, but is not necessarily limited to, anenergy attenuator 41, one or more energy monitors 43, and an active beampositioning mirror 45. The pulsed laser beam is directed from the lasersource 42 to the energy attenuator 41, then to the energy monitor 43,and then to the active beam positioning mirror 45. The active beampositioning mirror 45 directs the pulsed laser beam from the beammonitoring and processing module 44 to the beam delivery module 46.Using the energy attenuator 41 and energy monitor 43, the pulse energyof the pulsed laser beam may be varied to desired values. Additionally,the spatial separation of the focal points of the pulsed laser beam maybe varied by the beam monitoring and processing module 44.

The beam delivery module 46 scans the pulsed laser beam at the desiredscan region (e.g., the region 12). In one embodiment, the beam deliverymodule 46 includes, but is not necessarily limited to, a beam positionmonitor 47, an x-y scanner 49, a beam expander 52, one or more beamsplitters 54, and a z-scanning objective 56. The pulsed laser beam isreceived from the beam monitoring and processing module 44 by the x-yscanner 49 and directed to the beam expander 52, and the beam expander52 directs the pulsed laser beam to the z-scanning objective via thebeam splitter(s) 54. The z-scanning objective 56 can vary the focalpoint depth of the pulsed laser beam (e.g., from the anterior surface ofthe eye 31 or cornea to any depth within the eye 31 up to and includingthe retinal region).

Prior to initiating scanning or otherwise initiating photoalteration ofthe eye 31, the ophthalmic laser system 40 is coupled to the eye 31. Inone embodiment, the patient interface 33 provides a surface forcontacting the cornea of the patient's eye 31, which may also be used toapplanate the cornea. A suction ring assembly 53 or other device may beapplied to the eye 31 to fixate the eye prior to coupling the ophthalmiclaser system 40 to the eye (e.g., via the patient interface 33). In oneembodiment, the suction ring assembly 53 has an opening providing accessto the eye 31 when coupled thereto. The imaging system 34 may be used tofacilitate the coupling of the ophthalmic laser system 40 with the eye31. For example, by providing a real-time image of the fixated eye, theoperator can view the eye to properly center the output of the beamdelivery module 46 over the desired region 12.

Once the ophthalmic laser system 40 is coupled to the eye 31, theimaging system 34 may be used for alignment or centration of the laseroutput (e.g., the beam delivery module 46 output) and/or applanation ofthe cornea using the patient interface 33. The imaging system 34preferably provides a real-time, magnified, high resolution digitalimage of the eye 31 and includes, but is not necessarily limited to, animage sensor 57, an imaging interface 59, and an image processor 58coupled to the sensor 57 and the interface 59. An image of the eye 31 iscaptured using the image sensor 57 and displayed by the imaginginterface 59. In one embodiment, a high resolution digital camera (e.g.,a high-definition digital video camera based on charge coupled devices(CCDs) or the like) is used to capture the image and display the imageon the imaging interface 59.

Although FIG. 2 illustrates a combination of the image sensor 57 andbeam splitters 54 for capturing the image, the image sensor 57 may belocated in a variety of different positions or operate solely or operatewith additional optical elements to directly or indirectly captureimages of the eye 31. For example, the image sensor 57 may be locatedsubstantially adjacent to the z-scanning objective 56 to directlycapture images of the eye 31. In one embodiment, the image sensor 57 ismounted on a moveable gantry to vary the image focal plane captured bythe image sensor 57 and optically coupled with a variable aperture (notshown) (e.g., positioned between the image sensor 57 and the eye 31) forcontrolling the depth of focus and/or the amount of light sensed by theimage sensor 57. In another embodiment, at least one or more of a focuscontrol for varying the image focal plane captured by the image sensor57 and a focus depth control are incorporated into the image sensor 57.

The imaging interface 59 includes, but is not necessarily limited to, aninput device for operator selection of a variety of system parameters(e.g., associated with coupling the ophthalmic laser system 40 with theeye 31, image control, and the like) and a monitor displaying thereal-time, magnified, high resolution digital image of the eye 31. Theinput device may include one or more of a keyboard, a trackball, amouse, a touch-pad, a touch-sensitive screen, a joystick, a variablefocal length switch, a footswitch, and the like. In one preferredembodiment, the imaging interface 59 includes a touch-sensitive screendisplaying a graphical user interface for selecting the systemparameters and for viewing the alignment or centration of the laseroutput with reference to the desired region 12 of the eye 31 and/orviewing the applanation of the cornea. The graphical user interfaceprovides a variety of buttons, icons, or the like corresponding withdifferent functions for selection by the operator, and the operator mayselect a particular function by touching the corresponding buttondisplayed on the touch-sensitive screen. Examples of the differentfunctions that may be provided by the graphical user interface at theimaging interface 59 include, but are not necessarily limited to, adark/light eye function, an increase magnification function, a decreasemagnification function, an increase illumination function, a decreaseillumination function, an increase focal depth function, a decreasefocal depth function, the functions and system parameters provided bythe user interface 32, as previously described, and the like.

Operator control of the beam delivery module 46 alignment with the eye31, applanation of the cornea, and/or centration may be provided via theinput device of the imaging interface 59 or via a separate input device(e.g., a joystick). For example, the operator may control the raising,lowering, or lateral movement (two-dimensions) of the loading deck 35via the joystick while viewing the digital image of the eye 31 providedby the imaging system 34. The operator can adjust the lateral position(e.g., an x-axis position and a y-axis position) of the loading deck 35to align the output of the beam delivery module 46 with the eye 31 andlower the loading deck 35 (e.g., along a z-axis) to guide the patientinterface 33 into a pre-determined position with the suction ring 53(e.g., coupling the beam delivery module 46 with the eye 31). Anindicator may be displayed by the imaging interface 59 (e.g., a greenlight) when the beam delivery module 46 is properly coupled with the eye31 and/or when an applanation surface of the patient interface 33contacts the cornea. The operator may then applanate the cornea byfurther lowering the beam delivery module 46 (e.g., the loading deck 35and patient interface 33) using the input device, while monitoring thedegree of applanation as indicated by the digital image of the eye 31,and discontinuing movement of the beam delivery module 46 at a desireddegree of applanation determined by viewing the digital image of the eye31.

In one embodiment, a centration aid is displayed as an overlay on thedigital image of the eye 31 for assisting in centering the laser outputwith the desired region 12 of the eye 31 (e.g., to be photoaltered). Thecentration aid corresponds with the current position of the laser outputwith reference to the eye 31 (e.g., the two-dimensional position in thefocal plane of the pulsed laser beam and/or axial alignment of thepulsed laser beam with reference to an optical axis of the eye 31). Theoperator may align or center the laser output using the joystick orother input device. For example, by centering the centration aid withreference to the image of the pupil, the iris, or both the pupil andiris, displayed by the imaging interface 59, the operator may adjust theoutput of the beam delivery module 46 to be centered with reference tothe pupil, the iris, or both the pupil and iris. The centration aid mayalso be configured with reference to other anatomical indicators of theeye or other reference points. Following alignment or centration, theoperator may initiate scanning and photoalteration of the desired region12 of the eye 31.

The operator may continuously view the digital image of the eye 31provided by the imaging system 34 during alignment or centration,applanation, the entire process from initial fixation of the eye throughphotoalteration of the eye, or any other portion of such process. Forexample, the physician performing the ophthalmic laser procedure mayperform the ophthalmic laser procedure from fixation of the eye 31(e.g., using the suction ring assembly 53), through coupling of the beamdelivery module 46 to the eye 31 (e.g., via coupling of the patientinterface 33 with the suction ring assembly 53), through applanation ofthe cornea, through centration, and through photoalteration of thedesired region 12 of the eye 31, while maintaining viewing of thedigital image of the eye 31 provided by the imaging system 58. Thephysician does not have to switch from viewing the imaging interface 59to viewing the user interface 32 and/or does not have to switch fromviewing the imaging interface 59 to directly viewing the patient's eye.Using the imaging system 34 simplifies and enhances the physician'sfocus on the ophthalmic laser procedure by allowing the physician toview a single display for an entire ophthalmic laser procedure.

At times, the operator may desire a greater contrast between the pupiland the iris shown in the digital image of the eye 31 captured by theimaging system 34. In general, the image sensor 57 captures an initialdigital image of the eye 31 based on default settings. For example, inone embodiment, the image sensor 57 has a gamma function, which controlsthe intensity or brightness of each pixel of the digital image displayedby the imaging interface 59 based on the image detected by the imagesensor 57. The typical default is a linear gamma function, and the imagedetected by the image sensor 57 is displayed by the imaging system 34 onthe imaging interface 59 as with an intensity or brightness based on thelinear gamma function.

As previously mentioned, a user-selectable button is provided at theimaging interface 59 for activating the dark/light eye function. Whenthis function is selected (e.g., by touching a dark/light eye button onthe touch-sensitive screen), the image processor 58 modifies the gammafunction to a pre-determined setting (e.g., different from the default)and alters the intensity or brightness of the displayed image to enhancecontrast between the lower intensity or lower brightness levels. Thissetting may be selected such that darker-colors detected by the imagesensor 57 (e.g., brown eyes and black pupils) that are relatively closein intensity or brightness levels can be contrasted from one another toa greater degree than provided using the linear gamma function. Forexample, the image processor 58 retrieves a first set of intensity orbrightness values (associated with the default gamma function setting)from a look-up table (not shown), which is used to produce the initialdigital image of the eye 31. When the dark/light eye function isselected, the image processor 58 retrieves a second set of intensity orbrightness values (associated with a non-linear or greater than lineargamma function setting) from the look-up table, which is used to producean enhanced digital image of the eye 31 with greater contrast betweenthe pupil and iris, particularly suited for darker-colored eyes.

The darker-colors detected by the image sensor 57 are thus displayed bythe imaging interface 59 with a greater difference in relative intensityor brightness. In effect, selecting the dark/light eye function modifiesthe setting of the gamma function from the default setting to a settingthat is more sensitive to the changes in intensity or brightness fordarker-colored regions of the eye 31 as detected by the image sensor 57.For example a small change in intensity or brightness from onedarker-color to another darker-color detected by the image sensor 57produces corresponding pixels with a greater change in intensity orbrightness (e.g., greater than a linear change, such as two-foldincrease, a three-fold increase, a squared function, an exponentialfunction, and the like). The enhanced digital image of the eye 31provided by the dark/light eye function further assists the operatorduring centration, or any other portion of the ophthalmic laserprocedure, and is particularly suited for darker-colored eyes.De-selecting the dark/light eye function (e.g., by touching thedark/light eye button again) returns the gamma function setting to thedefault gamma function setting (e.g., linear).

In one embodiment, the image processor 58 is additionally coupled to theuser interface 32 to transmit the captured digital image of the eye 31to the user interface 32. In this embodiment, the digital image of theeye 31 may also be displayed by the user interface 32. Other functions,such as control of the various system parameters, may be transferred tothe imaging system 34. Similarly, functions provided by the imagingsystem 34, such as alignment or centration, may also be transferred tothe user interface 32.

FIG. 3 is a block diagram of an interface system 80 and the imagingsystem 34 shown in FIGS. 1 and 2 in accordance with one embodiment ofthe present invention. In this embodiment, the interface system 80includes, but is not necessarily limited to, the user interface 32having a touch-sensitive screen, a touch screen controller 84 coupled tothe user interface 32, and a central computing unit 86 coupled to theuser interface 32 and the touch screen controller 84. The centralcomputing unit 86 includes, but is not necessarily limited to, one ormore communication ports (e.g., USB ports), a network component 92(e.g., an Ethernet Gbit local area network (LAN) board), a videocomponent 90 (e.g., a video board) coupled to the user interface 82 viaa video input port (e.g., a cathode ray tube (CRT) mode input port), anda central processing unit (CPU) 88 (e.g., a CPU mother board). Thecentral computing unit 86 is also coupled to the user interface 32 viaone of the communication ports and to the touch screen controller 84 viaanother of the communication ports. The video component 90 receives avideo signal (e.g., a National Television System Committee (NTSC) videosignal) via an input port (e.g., an NTSC port) from the imaging system34. Thus, the user interface 82 may operate with the central computingunit 86 as a console and may operate to display digital video receivedfrom the imaging system 34.

The imaging system 34 includes, but is not necessarily limited to, theimaging interface 59 having a display 64, a touch screen controller 66coupled to the imaging interface 59, a brightness controller 70 coupledto the display 64, a processor 68 (e.g., a single board computer (SBC)with embedded board expandable (EBX) format and using a Pentium M 1.8GHz microprocessor produced by Intel Corp.) coupled to the brightnesscontroller (e.g., via an inverter port) and the touch screen controller,a data storage device 72 (e.g., a hard drive or the like) coupled to theprocessor 68, and the image sensor 57 coupled to the processor 68. Theimage sensor 57 is preferably a digital camera having a high resolution(e.g., 1624×1224 resolution) and more preferably has a resolution ofabout 2 megapixels or greater with a high frame rate (e.g., 1624×1224 atabout 20 frames per second or greater), such as the model GRAS-20S4M/Cdigital camera manufactured by Point Grey Research, Inc. The display 64may have a resolution (e.g., 1024×768 resolution) that is less than theresolution of the digital camera. In these embodiments, the informationcaptured by the high resolution digital camera is compressed by theprocessor 68 to the resolution of the display 64.

In this embodiment, the imaging interface 59 has a touch-sensitivescreen and a graphical user interface is displayed on the display 64 bythe processor 68. The processor 68 operates with the touch screencontroller 66 and brightness controller 70 to control or modify thebrightness level of the digital image of the eye when the dark/light eyebutton is selected. As previously described, the digital image of theeye captured by the image sensor 57 is displayed on the display 64 withan initial brightness level. For example, when the dark/light eye buttonis not selected, the processor 68 retrieves intensity or brightness datacorresponding with the default setting from a look-up table stored inthe data storage device 72.

The brightness level of the digital image may be modified when thedark/light eye button is selected. For example, the dark/light eyebutton may be displayed on the display 64 during operation of thegraphical user interface by the processor 68. When the dark/light eyebutton is selected (e.g., detected by the touch screen controller 66),the touch screen controller 66 transmits a signal to the processor 68indicating activation of the dark/light eye function. The processor 68retrieves intensity or brightness data corresponding with the dark/lighteye function from a look-up table stored in the data storage device 72and instructs the brightness controller 70 to modify the digital imagedisplayed on the display 64. In one embodiment, the dark/light eyefunction may have varying degrees of pre-determined contrast settings(e.g., corresponding with one or more of the different non-linear orgreater than linear gamma functions), and the graphical user interfacemay be modified with a slide feature, successive button-tap feature, orthe like, to provide operator selection of the different contrastsettings.

The graphical user interface may also provide selectable buttons, icons,or the like for operator control of focus and/or magnification of thedisplayed digital image of the eye. A first stepper/controller 76 iscoupled to the processor 68 to control the focus of the image sensor 57,and a second stepper/controller 78 is coupled to the processor 68 tocontrol the aperature of the image sensor 57. By detection (e.g., viathe touch screen controller 66) of a focus button (e.g., an increasefocus button or a decrease focus button) selection or a magnificationbutton (e.g., an increase magnification button or a decreasemagnification button) selection, the processor 68 instructs thestepper/controller 76, 78, respectively.

In one embodiment, the data storage device 72 stores one or moreapplications (e.g., containing computer readable instructions) that whenexecuted by the processor 68 cause the system 10, 40 to photoalter thedesired region 12 of the eye 31. For example, the application, whenexecuted, produces an initial digital image of the eye 31 having aninitial contrast between the iris and the pupil, increases (e.g., fromthe initial contrast) the contrast between the iris and pupil uponoperator selection of the dark/light eye function, displays a modifieddigital image of the eye 31 having the increased contrast the iris andpupil, centrates the eye 31 based on the increased contrast between theiris and pupil, and directs the pulsed laser beam at the desired region12. When producing the initial digital image (e.g., without activationof the dark/light eye function), the processor 68 retrieves brightnessdata from the data storage device 72 that corresponds with a defaultsetting (e.g., the default gamma function setting). To increase thecontrast between the iris and pupil, the processor 68 retrievesbrightness data from the data storage device 72 corresponding with amodified setting (e.g., the non-linear or greater than linear gammafunction setting). The modified digital image is produced based on thebrightness data corresponding with the modified setting.

The processor 68 is also coupled (e.g., with a LAN port) to the centralcomputing unit 86 via a network, such as Ethernet and/or a GigaLAN, andinformation (e.g., selected system parameters, graphical user interfacefunctions, and the like) may be transferred between the imaging system34 and the interface system 80.

FIG. 4 is a front view of a graphical user interface 94 in accordancewith one embodiment. The graphical user interface 94 may be used withthe imaging system 34 and/or the user interface 32 shown in FIGS. 1-3 todisplay a real-time, high resolution, digital image 95 of the patient'seye and provide a touch-sensitive screen for operator input. Thegraphical user interface 94 includes, but is not necessarily limited to,a focus control 99, a magnification control 98, preset focus depthbuttons 93 (e.g., Preset 1, Preset 2, and Preset 3), a dark/light eyebutton 97, and a window 87 displaying the digital image 95 of thepatient's eye. Additional buttons, icons, or the like may be provided bythe graphical user interface 94. In this embodiment, a centration aid 96is also displayed in the window 87 as an overlay on the digital image 95of the eye. Each of the focus and magnification controls 99 and 98,respectively, is a sliding button representation that may be controlledby operator touch and/or touch and slide (e.g., up or down). Duringcentration, the operator can touch the dark/light eye button 97 toenhance or increase the contrast between the pupil 97 and the iris 85 inthe digital image 95. This enhanced or increased contrast improves theoperator's ability to delineate between the pupil 85 and the iris 91 forcentering the centration aid 96 (e.g., aligning the centration aid 96with an outer boundary 89 of the iris 85). The centration aid 96 mayhave a variety of different configurations.

In another embodiment, one or more regions of the displayed digitalimage 95 of the eye may be selected to enhance the contrast therein. Forexample, a region for contrast enhancement may be selected by theoperator using a stylus, pen, or other device to contact thetouch-sensitive screen and/or circumscribe the desired regioncorresponding to the region of the displayed digital image 95 (e.g.,within the window 87).

FIG. 5 is a flow diagram of a method 100 for photoaltering a desiredregion of an eye using a pulsed laser beam in accordance with oneembodiment. A first digital image of the eye is produced having aninitial contrast between the iris and pupil, as indicated at step 105.For example, referring to FIGS. 1-4 and 5, an image of the eye 31 iscaptured with the image sensor 57 (e.g., a high resolution digitalcamera) and displayed using the graphical user interface 94 (e.g., inthe window 87) by the imaging system 34 (e.g., via the display 64 of theimaging interface 59). The image sensor 57 has a default linear gammafunction. In one embodiment, brightness data corresponding to thedefault linear gamma function and stored in a look-up table in the datastorage device 72 is retrieved by the image processor 68 to produce thedigital image of the eye 31 having the initial contrast (e.g., via thebrightness controller 70) on the display 64. The initial contrastbetween the iris and pupil is based on the default linear gammafunction. The contrast between the iris and pupil is selectivelyincreased to a greater contrast, as indicated at step 110. In oneembodiment, the contrast between the iris and pupil is increased uponoperator selection (e.g., activating the dark/light eye function, whichmay be provided as a touchable button 97). For example, brightness datacorresponding with a non-linear or greater than linear gamma functionand stored in a look-up table in the data storage device 72 is retrievedby the image processor 68. This brightness data enhances or increasesthe contrast between the iris and pupil in the digital image of the eyeand thus produces a digital image of the eye with enhanced or increasedcontrast (e.g., via the brightness controller 70 as instructed by theimage processor 68). A second digital image of the eye is displayed(e.g., via the display 64 of the imaging interface 59) having thegreater contrast, as indicated at step 115. The eye is centrated by theoperator based on this greater contrast between the iris and pupil, asindicated at step 120. The pulsed laser beam is directed at the desiredregion, as indicated at step 125.

Thus, systems 10, 40 and method 100 of photoaltering a desired region ofthe eye are provided that selectively enhances or increases the contrastbetween the iris and pupil displayed by the imaging system 34. Examplesof some refractive eye surgery applications for the systems 10, 40and/or method 100 include, but are not necessarily limited to,photorefractive keratectomy (PRK), LASIK, laser assisted sub-epitheliumkeratomileusis (LASEK), or the like. Using the imaging system 34 of thesystems 10, 40 and method 100 enhances contrast and facilitates operatorcentration or alignment of the laser output with the patient's eye(e.g., in the desired region of photoalteration).

While embodiments of this invention have been shown and described, itwill be apparent to those skilled in the art that many moremodifications are possible without departing from the inventive conceptsherein. The invention, therefore, is not to be restricted except in thespirit of the following claims.

What is claimed is:
 1. A system for photoaltering a region of an eye,the eye having a pupil and an iris, the system comprising: a laserassembly configured to output a pulsed laser beam; a user interfaceincluding a user-selectable light/dark eye control, wherein the systemis configured such that, in response to the user-selectable light/darkeye control not being selected by a user, the system displays via theuser interface a first digital image of the eye having a first contrastbetween the pupil and the iris, and wherein the system is furtherconfigured such that, in response to the user-selectable light/dark eyecontrol being selected by the user, the system displays via the userinterface a second digital image of the eye having a second contrastbetween the pupil and the iris which is different than the firstcontrast; and a controller coupled to the laser assembly and the userinterface, the controller configured to: selectively change the firstcontrast between the pupil and the iris to the second contrast betweenthe pupil and the iris in response to the user-selectable light/dark eyecontrol being selected by the user to generate the second digital imagefor display by the user interface; and direct the pulsed laser beam tothe region of the eye based on the first digital image in response tothe user-selectable light/dark eye control not being selected by theuser, and based on the second digital image in response to theuser-selectable light/dark eye control being selected by the user. 2.The system of claim 1, wherein the controller is further configured toadjust a centration of the eye to align the pulsed laser beam with theeye based on the second digital image prior to directing the pulsedlaser beam to the region of the eye in response to the user-selectablelight/dark eye control being selected by the user.
 3. The system ofclaim 1, wherein the user interface is further configured to display acentration aide overlaying the second digital image of the eye inresponse to the user-selectable light/dark eye control being selected bythe user; wherein the controller is further configured to position thecentration aide into an alignment with respect to the pupil and the irisin response to a user input; and wherein the controller is configured todirect the pulsed laser beam to the region of the eye based on thealignment of the centration aide with respect to the pupil and the iris.4. The system of claim 1, further comprising a sensor coupled to thecontroller, the sensor configured to transmit image data to thecontroller; wherein the controller is further configured to, in responseto the user-selectable light/dark eye control not being selected, selecta first brightness data corresponding with the image data to generatethe first digital image, the first contrast based on the firstbrightness data; and wherein the controller is configured to selectivelychange the first contrast to the second contrast in response to theuser-selectable light/dark eye control being selected by selecting asecond brightness data corresponding with the image data to generate thesecond digital image, the second contrast based on the second brightnessdata.
 5. The system of claim 4, further comprising a memory coupled tothe controller, the memory configured to store a look-up table of apre-determined first correspondence between a set of input values and afirst set of output values and a pre-determined second correspondencebetween the set of input values and a second set of output values; andwherein the controller is configured to select the first brightness databy using the image data as input values for the look-up table toretrieve corresponding first output values as the first brightness data;and wherein the controller is configured to select the second brightnessdata by using the image data as input values for the look-up table toretrieve corresponding second output values as the second brightnessdata.
 6. The system of claim 4, wherein the first brightness datacorresponds to a linear brightness function, and wherein the secondbrightness data corresponds to a non-linear brightness function.
 7. Thesystem of claim 1, wherein the user interface comprises atouch-sensitive screen, and the user-selectable light/dark eye controlcomprises a button displayed on the touch-sensitive screen.
 8. Thesystem of claim 1, wherein the user-selectable light/dark eye controlcomprises a voice recognition device.
 9. The system of claim 1, furthercomprising a sensor coupled to the controller, the sensor configured totransmit first image data to the controller, the first contrast based onthe first image data; wherein the controller is further configured togenerate the first digital image using the first image data in responseto the user-selectable light/dark eye control not being selected; andwherein the controller is configured to selectively change the firstcontrast to the second contrast by modifying at least some of the firstimage data to produce second image data and generating the seconddigital image using the second image data in response to theuser-selectable light/dark eye control being selected by the user, thesecond contrast based on the second image data.
 10. The system of claim9, wherein the sensor is further configured to capture the first digitalimage of the eye with a gamma function, the gamma function having adefault setting, the first contrast based on the default setting; andwherein the controller is further configured to modify the gammafunction from the default setting to increase the first contrast to thesecond contrast.
 11. The system of claim 10, wherein the default settingis a linear function; and wherein the controller is further configuredto modify the gamma function to a non-linear function.
 12. The system ofclaim 11, wherein the non-linear function is based on a set ofpre-determined brightness values corresponding with a set of sensedbrightness values.
 13. The system of claim 1, further comprising: adigital camera having an image sensor configured to capture image datafor the eye; a data storage device; and wherein the digital camera has agamma function setting which converts a brightness of portions of theimage data captured by the image sensor to a brightness of each pixeldisplayed on the user interface, wherein the first digital image havingthe first contrast is produced based on the gamma function setting ofthe digital camera which is set to a linear default gamma functionsetting, and wherein the user-selectable light/dark eye control isconfigured to be activated by a user to increase the first contrastbetween the iris and the pupil to the second contrast by modifying thedigital camera's gamma function from the linear default setting to anon-linear function that enhances contrast of the pixels displayed onthe user interface between the pupil and darker colored irises, whereinthe non-linear function increases the contrast of the pixels displayedon the user interface between the pupil and darker colored irises basedon values in a look-up table stored in the data storage device.